1. Field of Invention
The invention relates to a wiper blade for a wiper apparatus incorporated in automobiles and/or vessels.
2. Description of Related Art
Generally, this type of wiper blade is attached to the tip end portion of a wiper arm via a connection member, and is resiliently brought into contact with a window surface on the basis of a pressing force of a resilient pressing mechanism disposed at the wiper arm or wiper blade. As the wiper blade reciprocates, reverses its moving direction or swings in this state, the window surface is wiped off. In such a type of wiper blade, the center part of the wiper blade in its longitudinal direction is connected to the connection member of the wiper arm, the wiper blade is pressed toward the window surface side via the connection member. Therefore, the pressing state of the wiper blade onto the window surface at the base part, intermediate part and tip end part in the longitudinal direction thereof in the process of wiping movement is made roughly the same if the window surface is flat. Accordingly, the error angle of a lip portion of the wiper blade, which becomes the contacting part of the wiper blade with the window surface, never changes greatly even at the above-described base part, intermediate part and tip end part. As a result, satisfactory wiping operations can be achieved.
The error angle is an angle that is formed by the centerline of the wiper blade and the normal line of the window surface at the portion of the window surface with which the lip portion is brought into contact. The error angle is established by the pressing direction of the lip portion to the window surface and the above-described normal line. The established error angle is set by expressing in which direction the wiper blade lies with respect to the normal line, in terms of positive or negative figures showing the corresponding direction. The wiping operations of the wiper blade will be made more favorable as a difference in the error angles becomes smaller and smaller at respective parts in the longitudinal direction of the wiper blade. In addition, it is favorable that the error angle is set so that it can be made into either one of the positive or negative figures at the respective parts of the wiper blade in the longitudinal direction, that is, so that the lying direction thereof is made into the same.
On the other hand, there are cases where the window surfaces are curved, wherein generally, the curvature ratio becomes larger and larger toward both right and left end parts, in comparison with the central portion. Both the end parts are curved so as to be erected further than the central portion. In the case of wiping off such a curved window surface, the pressing states of the wiper blade onto the window surface at the respective parts, such as the base part, intermediate part and tip end parts, differ from each other due to the curvature and erecting state to which the wiper blade is subjected in the process of the wiping movement. Therefore, the error angle becomes different at the respective parts. Moreover, where the wiper blade presses the window surface having a curvature in the vertical direction and the right and left directions so as to cross a ridge, i.e., a much more curved part, in an inclined state, the pressing direction of the wiper blade onto the window surface may differ at both end parts in the longitudinal direction thereof. If so, the error angles thereof become reverse figures of each other in terms of positive and negative, and the lying directions of the lip portion with respect to the supporting part may be made inverse (opposed to each other) at both end parts.
A wiper apparatus as shown in FIG. 2(A) is structured so that it has swinging axis parts of the wiper arms supported at one side part and the central part of the curved window surface described above. A pair of wiper blades, one for the driver""s seat and the other for the passenger""s seat, are attached to the swinging axis parts. In such a wiper apparatus, the swinging axis part of the wiper blade for the driver""s seat is located at one side part of the window surface. In this case, the wiper blade of the wiper arm that is attached at the swinging axis part for the driver""s seat may be disposed approximately at the central part of the window surface, wherein there is no large difference in respective error angles since the curvature of the window surface is small at the lower reversing position of the wiper blade. However, as the wiper blade comes to the end part side of the window surface, approaching the upper reversing position, the error angle at both end parts in the longitudinal direction becomes smaller in comparison with that at the intermediate part. To the contrary, generally, the wiper blade of the wiper arm attached at the swinging axis part of a wiper apparatus for the passenger""s seat, which is positioned at the central part of the window surface, is disposed near the end part of the central part of the window surface. Therefore, the error angles at both of the tip end part and the base part at the upper and lower reversing positions of the wiper blade, as in the graph shown in FIG. 7, become reverse (positive and negative) figures centering around the intermediate part. As a result, the difference in the error angle at the respective parts tends to increase.
Thus, in the case where the error angles at both end parts in the longitudinal direction becomes reverse (positive and negative) figures centering around the central part, although the wiper blade is such that the error angles at the respective parts may change due to the relationship between the corresponding wiper blade and the profile (curvature) of the window surface, a problem occurs in that the wiping performance cannot be sufficiently displayed. Further, in the case where the wiper blade is maintained at the lower reversing position when the wiper apparatus is not used, the difference in the error angle at the respective parts is large, as described above, at the wiper blade for the passenger""s seat, resulting in the error angles at both end parts in the longitudinal direction becoming reverse (positive and negative) figures centering around the intermediate part. When the wiper apparatus is not used, the wiper blade is pressed to the window surface in a resiliently pressed state for a long time subjecting the blade rubber to abnormal deformation, wherein abnormal noise is generated in wiping operations and the blade rubber may be liable to excessive wear. The invention aims to solve the above-described problems.
The invention was developed to solve the problems and other shortcomings in terms of the above-described situations. It is therefore an object of the invention to provide a wiper blade, attached to the tip end part of a wiper arm via a connection part, which reciprocates, inverses its moving direction, or swings in a state where the above-mentioned wiper blade is resiliently brought into contact with a window surface by a resilient pressing mechanism disposed at the above-mentioned wiper arm. The wiper blade is constructed so as to wipe off the above-mentioned window surface. The above-mentioned wiper blade includes a lip portion that protrudes at least toward the window surface and is able to change the posture thereof to a risen posture erect from the above-mentioned window surface and to a lain posture turned down on the above-mentioned window surface. The wiper blade further includes a resilient member that presses the above-mentioned lip portion so as to be brought into close contact with the above-mentioned window surface. The resilient member includes a posture-correcting portion, which is provided with a twisting feature to correct both end parts of the above-mentioned lip portion in its lengthwise direction with respect to each other by returning the above-mentioned resilient member to its natural state. Thereby, the lip portion of the wiper blade is corrected with respect to its lengthwise posture, and the wiper blade can be provided with an adequate error angle over the full length of the blade.
In such a wiper blade, the above-mentioned resilient member is a long plate spring, or a pair of parallel plate springs, and the above-mentioned posture-correcting portion is formed at both the tip end portions of the above-mentioned plate springs.
Further, in such a wiper blade, the above-mentioned resilient member is a long plate spring, and the above-mentioned posture-correcting portion is formed over the full length in the lengthwise direction of the above-mentioned plate spring.
Still further, in such a wiper blade, the above-mentioned resilient member is made rectilinear against a pressing force of the above-mentioned resilient member to cause the above-mentioned lip portion to be erected to a risen posture.
Yet still further, in such a wiper blade, the above-mentioned risen posture of the lip portion may be substantially perpendicular to the window surface over the full length of the wiper blade. Moreover, the lip portion may be protrudingly attached to the resilient member so that the lip portion may become substantially orthogonal to the plate surface of the resilient member.
Finally, in such a wiper blade, the resilient member may be curved further in a longitudinal direction such that the resilient member""s natural state of curvature exceeds the maximum curvature of the window surface.